This invention relates to a pipe bending machine with a bending tool, a pipe feed by means of which a pipe that is to be bent can be advanced along its longitudinal axis towards the bending tool, a pipe holder that is guided in the longitudinal direction of the pipe in a linear guide unit provided on the machine base and movable by a pipe feed drive system with a drive mechanism mounted on the machine base, and a mandrel retractor by which a bending mandrel mounted on a mandrel bar that extends in the longitudinal direction of the pipe on the bending tool side can be moved back and forth in the axial direction of the pipe between a working position and a retracted position. The mandrel retraction device includes a mandrel bar support that is guided in the longitudinal direction of the pipe by a linear guide unit provided on the machine base and can be moved by means of a mandrel bar drive unit operated by a drive system located on the machine base.
A pipe bending machine of this type is known and has been described in DE-A-40 10 445. In this prior art system, the pipe to be bent is clamped between a bending template and the clamping jaw of a bending tool and is then shaped by turning the bending template and rotating the clamping jaw around a bending axis. The pipe is advanced relative to the bending tool by means of a pipe feed with a feed carriage that can be moved in the longitudinal direction of the pipe. The carriage is equipped with a clamping sleeve that holds the pipe at its far end spaced from the bending tool. The feed carriage of this prior art pipe bending machine is moved in the longitudinal direction of the pipe by a toothed belt driven by a motor mounted on the machine base. In the direction of its linear travel, the feed carriage is guided by guide rollers that are themselves controlled by a longitudinal guide on the machine base.
A bending mandrel that, when in its working position next to the bending tool, is inserted in the pipe to be bent, making certain that during the bending process the cross-sectional profile of the pipe is not deformed. Just before a bending process is completed, the bending mandrel is pulled back from its working position into a retracted position and thus moved away from the bending tool. The bending mandrel is mounted at the end of a mandrel bar that extends on the bending-tool side in the longitudinal direction of the pipe. The mandrel bar extends through the entire feed carriage of the pipe feed unit and is held in place in a mounting on the side of the latter facing away from the bending tool. For moving the bending mandrel, the mounting with the mandrel bar retained by it travels in the longitudinal direction of the pipe under the action of a piston and cylinder assembly attached to the machine base.
To move the feed carriage and the bending mandrel, this prior art design is relatively complex. Moreover, the movement of the mandrel bar mount in the longitudinal direction of the pipe is spatially very restricted.
It is therefore the objective of this invention to improve the prior art design by providing a novel bending pipe machine with a common linear guide system and/or common drive system for the mandrel bar support and pipe holder.